Aerial rockets and missiles which include folded, deployable guidance wings have been in use at least since the late 1940's, with the FFAR (Folding Fin Aerial Rocket) being used in the Korean and Vietnam conflicts, and the more recent Hydra 70 family of WAFAR (Wrap-Around Fin Aerial Rocket) and Advanced Precision Kill Weapon System (APKWS) laser guided missile. For many such weapons, the guidance wings are folded in a stowed configuration within the main fuselage until the weapon is launched, at which point the wings deploy outward through slots provided in the fuselage.
Typically, a rocket or missile is spun during its flight for increased accuracy and stability. For many missiles and rockets with folded, deployable guidance wings, the guidance wings are released from their folded and stowed configuration upon launch, and are deployed by the centrifugal force which results from the spinning of the weapon in flight. In some cases, the wing slots are covered by frangible seals which protect the interior of the missile from moisture and debris during storage, transport, and handling. In these cases the guidance wings must be deployed with sufficient initial force to enable them to penetrate the seals.
Clearly, wing deployment through frangible cover seals becomes more dependable as the initial deployment force is increased. However, there is a practical limit to how rapidly a missile can be spun. In one example, the average centrifugal force on the tip of a guidance wing at the beginning of deployment is only approximately 7.7 pounds at the minimum spin rate. This amount of centripetal energy may not be sufficient by itself to enable the wings to burst through the frangible slot covers. As a result, some weapons that include deployable folded guidance wings and frangible wing slot covers have demonstrated a tendency for the guidance system to fail due to a lack of proper guidance wing deployment. This problem can be addressed by a wing deployment initiator, which assists the deployment of the guidance wings by providing an initial burst of energy to help the wings break through the frangible covers.
In some designs, the wing deployment initiator uses explosives to push the wings through the frangible covers. However, this approach can be undesirable due to the violent forces produced by the explosives, and due to concerns about the safety and the long-term chemical stability of the explosives during storage of the weapon.
A mechanical solution would be desirable. However, only very limited space is available for a wing deployment initiator to occupy. Also, the weight of the deployment initiator must be as low as possible. Therefore, it can be very difficult to provide a mechanical wing deployment initiator which can provide sufficient force to enable the guidance wings to break through the frangible covers while also fitting within the available space and remaining sufficiently light in weight.
What is needed, therefore, is a mechanical wing deployment initiator which will not add excessive weight to a missile or rocket, will fit within available space within the guidance wing storage region of the missile or rocket, and will provide sufficient added force during the initial guidance wing deployment so as to ensure that the wings are reliably able to burst through frangible wing slot cover seals and be fully deployed.